Enzymes

• Catalyst: a substance that speeds up a chemical reaction and is not changed by the reaction
• Enzymes: proteins that function as biological catalysts
• Enzymes lower the amount of energy needed for reaction to take place
• Lock and key theory

  
• Substrate: the molecule(s) before they are made to react
• Product: the molecule(s) that are made in a reaction
• Catabolic reaction: molecules are broken down
• Anabolic reaction: molecules are combined
• Enzymes have an optimum temperature: the temperature at which they work best giving the fastest reaction ≈ 37 °C in animals
• When temperature increases, molecules move faster so collide with an enzyme in less time
• Having more energy makes enzymes more likely to bind to active site.
• If temperature is too high, enzyme molecules vibrate too vigorously and enzyme is denatured; it loses its shape and will no longer bind with a substrate.
• When the temperature is too low there is not enough kinetic energy for the enzyme reaction so it reacts too slowly.
• Some enzymes work best in an acid and others in an alkaline
• Enzymes work best at their optimum pH
• If the pH is changed then the enzyme will denature and will no longer fit with substrate- no reaction takes place
• Effect of temperature on enzyme activity

  
• Effect of pH on enzyme activity

  
• Enzymes lower the activation energy needed for reaction to take place